<template>
	<view>
		<view class="title">请在下面输入签名：</view>
		<canvas class="mycanvas" canvas-id="mycanvas" @touchstart="touchstart" @touchmove="touchmove"
			@touchend="touchend"></canvas>
		<view class="footer">
			<view class="left" @click="finish">完成</view>
			<view class="right" @click="clear">清除</view>
		</view>
		<image :src="url"></image>
	</view>
</template>

<script>
	export default {
		data() {
			return {
				ctx: "", // 绘图图像
				points: [], // 路径点集合
				url: ""
			};
		},
		onLoad() {
			this.ctx = uni.createCanvasContext("mycanvas", this); // 创建绘图对象
			// 设置画笔样式
			this.ctx.lineWidth = 2;
			this.ctx.lineCap = "round";
			this.ctx.lineJoin = "round";
			this.ctx.strokeStyle = "#ff0000";
		},
		methods: {
			// 触摸开始，获取到起点
			touchstart(e) {
				const startX = e.changedTouches[0].x;
				const startY = e.changedTouches[0].y;
				const startPoint = {
					X: startX,
					Y: startY
				};
				this.points.push(startPoint);

				// 每次触摸开始，开启新的路径
				this.ctx.beginPath();
			},

			// 触摸移动，获取到路径点
			touchmove(e) {
				const moveX = e.changedTouches[0].x;
				const moveY = e.changedTouches[0].y;
				const movePoint = {
					X: moveX,
					Y: moveY
				};
				this.points.push(movePoint); // 存点
				if (this.points.length >= 2) {
					this.draw(); // 绘制路径
				}
			},

			// 触摸结束，将未绘制的点清空防止对后续路径产生干扰
			touchend() {
				this.points = [];
			},

			/* ***********************************************
			#   绘制笔迹
			#	1.为保证笔迹实时显示，必须在移动的同时绘制笔迹
			#	2.为保证笔迹连续，每次从路径集合中区两个点作为起点（moveTo）和终点(lineTo)
			#	3.将上一次的终点作为下一次绘制的起点（即清除第一个点）
			************************************************ */
			draw() {
				const point1 = this.points[0];
				const point2 = this.points[1];
				this.points.shift();
				this.ctx.moveTo(point1.X, point1.Y);
				this.ctx.lineTo(point2.X, point2.Y);
				this.ctx.stroke();
				this.ctx.draw(true);
			},

			// 清空画布
			clear() {
				const that = this;
				uni.getSystemInfo({
					success(res) {
						const canvasw = res.windowWidth;
						const canvash = res.windowHeight;
						that.ctx.clearRect(0, 0, canvasw, canvash);
						that.ctx.draw(true);
					}
				});
			},

			// 完成绘画并保存到本地
			finish() {
				const that = this;
				uni.canvasToTempFilePath({
					canvasId: "mycanvas",
					success(res) {
						that.url = res.tempFilePath;
						// uni.saveImageToPhotosAlbum({
						// 	filePath: res.tempFilePath
						// });
					}
				});
			}
		}
	};
</script>

<style>
	.title {
		height: 50upx;
		line-height: 50upx;
		font-size: 16px;
	}

	.mycanvas {
		width: 100%;
		height: calc(80vh - 200upx);
		background-color: #ECECEC;
		border: 1px dotted black;
		touch-action: none;
	}

	.footer {
		font-size: 16px;
		height: 150upx;
		display: flex;
		justify-content: space-around;
		align-items: center;
	}

	.left,
	.right {
		line-height: 100upx;
		height: 100upx;
		width: 250upx;
		text-align: center;
		font-weight: bold;
		color: white;
		border-radius: 5upx;
	}

	.left {
		background: #007AFF;
	}

	.right {
		background: orange;
	}
</style>